Fix builder/parser so it keeps some whitespace on split lines.

If previous line ends with whitespace, or next line starts with whitepsace
we need to preserve a space otherwise things line:
RUN echo\
   hello
will appear as: RUN echohello

Noticed this while looking at #5744 because he had lines ending in &&\

Signed-off-by: Doug Davis <dug@us.ibm.com>

builder/parser/parser.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"regexp"
 	"strings"
+	"unicode"
 )
 
 // Node is a structure used to represent a parse tree.
@@ -96,14 +97,14 @@ func Parse(rwc io.Reader) (*Node, error) {
 	scanner := bufio.NewScanner(rwc)
 
 	for scanner.Scan() {
-		line, child, err := parseLine(strings.TrimSpace(scanner.Text()))
+		line, child, err := parseLine(strings.TrimLeftFunc(scanner.Text(), unicode.IsSpace))
 		if err != nil {
 			return nil, err
 		}
 
 		if line != "" && child == nil {
 			for scanner.Scan() {
-				newline := strings.TrimSpace(scanner.Text())
+				newline := scanner.Text()
 
 				if newline == "" {
 					continue

builder/parser/parser_test.go

@@ -71,8 +71,8 @@ func TestTestData(t *testing.T) {
 		}
 
 		if ast.Dump()+"\n" != string(content) {
-			fmt.Fprintln(os.Stderr, ast.Dump())
-			fmt.Fprintln(os.Stderr, string(content))
+			fmt.Fprintln(os.Stderr, "Result:\n"+ast.Dump())
+			fmt.Fprintln(os.Stderr, "Expected:\n"+string(content))
 			t.Fatalf("%s: AST dump of dockerfile does not match result", dir.Name())
 		}
 

builder/parser/testfiles/continueIndent/Dockerfile

@@ -0,0 +1,28 @@
+FROM ubuntu:14.04
+
+RUN echo hello\
+  world\
+  goodnight  \
+  moon\
+  light\
+ning
+RUN echo hello  \
+  world
+RUN echo hello  \
+world
+RUN echo hello \
+goodbye\
+frog
+RUN echo hello  \  
+RUN echo hi \
+ \
+ world \
+\
+ good\
+\
+night
+RUN echo goodbye\
+frog
+RUN echo good\
+bye\
+frog

builder/parser/testfiles/continueIndent/result

@@ -0,0 +1,9 @@
+(from "ubuntu:14.04")
+(run "echo hello  world  goodnight    moon  lightning")
+(run "echo hello    world")
+(run "echo hello  world")
+(run "echo hello goodbyefrog")
+(run "echo hello  \\")
+(run "echo hi   world  goodnight")
+(run "echo goodbyefrog")
+(run "echo goodbyefrog")